Method of making dies



Oct. 31, 1933. Q STEVENS I 1,932,426

Patented Oct. 31, 1933 UNITED STATES PATENT OFFICE 8 Claims.

This application is a continuation in part of my co-pending applicationSerial Number 455,838,

filed May 26, 1930.

This invention relates to dies and the method of making the same, andparticularly to a method of making dies by the type method asdifferentiated from the method of making dies by removing the necessarystock from a block of hardenable die material .to form the desireddepression therein.

Ano'v her object is to. provide a method'of making dies comprising infirst making a master die, thereafter employing the master die to make amale die or type member, and thereafter employing the male die or typemember to form a female die member by forcing the male memberrinto thefemale member to cause the desired depression to be formed therein, andthereafter employing the female member for productive purposes.

Another object is to provide a method as above described in which themaster die is constructed to provide for a triple shrinkage, resultingin a double shrinkage being provided on the male die or type member, anda single shrinkage resulting in the die to be employed for produc'ion.

Another object is to provide a method of press ing a male die memberinto a block of die stock .0 form a complementary female membercomprising in heating the block of stock beyond its critical temperatureand maintaining it against oxidization while pressing the male memberthereinto.

Another object is to provide a method of pressing a male die member intoa block of die stock to form a complementary female member comprising inheating the block 'of stock beyond its critical temperature and limitingit against lateral spreading while pressing the male member thereinto.

Another object is to provide means for forming on or in a die block, aprojection or depression complementary to a preformed depression orprojecfion, comprising the provision of a die member having formedtherein or thereon a depression or projection complementary to theprojection on or depression in the die desired, providing a retainingwall about such die member, and then pressing a heated block of diestock against said preformed member while said block of die stock islaterally supported by said retaining wall.

Anolher object is to provide a die half comprising an insert retainingdie block provided with a recess therein, and an insert secured in the amethod by which the master die may be recess.

Another object is to provide a die half comprising an insert retainingdie block provided with a. recess therein, and an insert secured in therecess by shrinkage of the retaining die block.

Another object is to provide an insert retaining die block as abovedescribed with a knock-out pin for each insert.

Another object is to provide a simple and economical method of changingthe shape of a die by a welding process after the die has beencompleted.

Another object is to provide a method of adding material to a die afterthe die has been completed, comprising in depositing metal of thedesired analysis over the desired areas of the die by a welding processcarried on in a reducing or non-oxidizing atmosphere, and thenre-machining the depression.

Another object is to provide a method of forming dies in which anypossibility of the distortion of the die surface due to the flowing ofthe metal 7 to form a flash is obviated.

Other objects will be apparent or will be spe cifically pointed out inthe following specification, reference being had to the accompanyingdrawings, in which- 30 Fig. 1 is a front elevation of a more-or-lessimaginary object which it may be desired to form.

Fig. 2 is a vertical sectional view taken centrally through a master dieinsert prepared in accordance with the present invention for forming thearticle shown in Fig. 1.

Fig. 3 is a more or less diagrammatic vertical sectional view takencentrally through the die blocks of a power press or power hammershowing the master die illustrated in Fig. 2 supported in the upper diemembers and illustrating a male die member or type as having been formedtherefrom and as being suported in the lower die member.

Fig. 4 is a perspective view of the male die insert member or type whichis formed by the operation illustrated in Fig. 3, after it has beenfinish machined.

Fig. 5 is a view similar to Fig. 3 illustrating the manner in which themale die member or type is employed for forming the die insert block tobe employed for productive purposes.

Fig. 6 is a view similar to Figs. 3 and 5 illustrating the position inwhich the die insert blocks assume in the hammer or press to form thearticle illustrated in Fig. 1.

Fig. '7 is a view similar to Fig. 2 illustrating changed in shape afterhaving been once completed and without afiecting its accuracy or Thereare numerous advantages to be derived by forminga die by pressing a typeinto a suit- T able block or stock, over the conventional meth- 0d, suchas for instance, relative cheapness, but more important is the fact thatby the conventional method the depression in being cut necessarilyexposes the ends of the fibrous structure of the metal in the walls ofthe depression, and the ends of these fibers break down relatively fastdue to the washing action of the metal being forged therein. In formingsuch dies by pressing into the stock from which theyare made a malemember or type, the fibers of the block are not severed at any time butare merely bent to accommodate the shape of the type, and consequentlyno exposed fiber endsare present in the die depression which will fosterbreaking down of the depression and consequent destruction of the diemember.

To my knowledge no method has heretofore been proposed forsatisfactorily accomplishing, in a commercial way, the production of dieblocks made by forcing a type into a block of die stock, but there areseveral reasons for this, as will hereinafter be brought out in thefollowingspecification.

Heretofore it has been the conventional practice in making dies toprovide a relatively thick block of stock of a size approximating thehead or table of the hammer or press in which the forging is to beaccomplished, and then form the depression in such block of stock. Thisnot only necessitates the handling of a relatively large and heavy block.of stock during forming of the dies, but when the dies have become wornto a point where they must be recut or replaced, it is necessary torecut the depression or scrap the entire block.

In accordance with the present invention, instead of following theconventional practice, I provide a block of stock of a size andthickness commensurate with that conventionally employed, and removefrom the central portion thereof sufiicient metal to form a recess or depression whose dimensions are larger by definite amounts per unit oflength than the corresponding dimensions of the depression desired inthe final die, and then form a block of die stock of a size commensuratewith this recess and form the die depression in this block of stock, andthereafter secure this block of stock into the large block, therebyproviding an insert which may be removed and recut if desired, (orreplaced as occasions of wear or other conditions dictate, and therebyeliminate not only the handling of the large block during machiningoperations upon the die depression, but further eliminate the wasteoccasioned in conventional constructions by scrapping the entire blockupon excessive wear of the die depression. q

Furthermore, in accordance with the present invention I provide a methodbywhich an inmessa e numerable number of objects may be forged orotherwise formed by dies with the assurance that all of the objects willbe identical with each other.

For the purpose of illustrating the present invention I have illustratedin the accompanying drawings an article 10 which may be consideredmore-or-less imaginary as far as actual use is concerned, but which isentirely sufficient for explaining the essential of the presentinvention. It may be noted that it is considered that the article 10 iscircular in cross-section, and consequentlyis identical in size andshape on both sides of a plane including its axis.

In accordance with the present invention, in making dies to forge, forinstance, the article 10, a block 11 of hardenable die metal, asindicated in Fig. 2, of a size substantially greater than the article 10as indicated, is worked upon in accordance with conventional practice,that is, by drilling, chipping, grinding and the like, so as to providein one face thereon a depression 12 complementary in shape to one-halfof the article 10,. but with this difference,that a triple shrinkage isprovided for in making the depression 12.

In Fig. 3 I illustrate the bed 13 and head 14 of a power press, forginghammer or the like, and the head 14 is provided with an insert retainerdie block member 15, this member corresponding tion of the recess 16,however, are tapered slightly outwardly as at 1'7 an amountcorrespondingwith the draft conventionally employed in connection withforging or other corresponding dies. The depth of the upper portionhaving the parallel sides corresponds substantially exactly with thedepth of the master die 11 and the dimensions of the same are such thatthe retainer die block 15 may be suitably heated to expand it, and themaster die 11 be inserted therein firmly against the bottom of the sameand be securely held therein by shrinkage of the retainer die block 15when cooled.

The bed or table 13 of the press or hammer is provided with a block 18similar to the block 15 and the upper surface thereof is provided with arecess 19 of the same size and shape as the portion 17 of the recess 16,but opposed in relation thereto. In other words, its depth isapproximately the same depth, although this is not essential, to thedepth of the portion 17 of the recess 16, and its side walls taperoutwardly from the bottom of the recess to provide the draftconventionally provided for in such dies. It may be noted, however, thatit is not necessary that the side walls of the recess 19 be formedtapered .as shown, butif desired they may be formed normal to the uppersurface of the block 18 for, as will be apparent, when a mass of heatedmetal as hereinafter described is forged into the recess 19, the objectformed thereby will, in cooling,

naturally loosen itself in the recess 19 due to its the exception thatin a suitable electric furnace under the influence of "a reducingatmosphere, is then placed in the recess 19 while still protected in anysuitable manner against oxidization, and the head 14 of the press orhammer is then brought down towards the bed or placed within thedepression 19 to not only completely fill the depression 19 but alsothat part of the depression 16 not filled with the metal of the masterdie 11, and it is to be, noted that during this operation the taperedwalls 17 of the recess 16 serve to retain the metal being worked uponagainst lateral expansion, and thus insures not only a complete fillingof the depression 12 in the master die 11, but also insures a properpressing and working of the mass of metal so as to maintain the qualityof the crystalline structure therebf. The critical temperature of themetal is that temperature at which transmission from the crystallinestate to that of a solid solution occurs. The amount of metal which isplaced within the recess 19 may be readily predetermined so that verylittle if any flash or fin is formed upon the same during this process.

The result is the provision of a block 20 having formed thereon a type21 which is complementary in shape and size to the depression 12 in themaster die 11, the only difference being that when the type 21 hascooled it is smaller than the depression 12 byan amount equal to theshrinkage of the metal in cooling. In other words, as the depression 12has been formed to compensate for a" triple shrinkage, the type 21 willbe formed to compensate for a double shrink age. The block 20 with thetype 21 formed thereon may now be removed from the depression 19 as bymeans of a stepped knockout pin 22 which may be provided in the/bed 13and block 18 and with its enlarged head positioned in normally flushrelation with respect to the bottom of the recess 19. A similar knockoutpin :23 may be provided in the head 14 and block 15 if desired so as tofacilitate removal of the master die 11 from the recess 16 upon.suitably heating the block 15.

The block 20 with the type 21 thereon is then preferably machined on theside and bottom faces thereof so as to bring the block 20 to the properexternal dimensions, that is, in length, width and thickness, and'withthe side walls 20 preferably normal to and the face preferably parallelto the top surface thereof as indicated in Fig. 4. It is then hardenedin any suitable manner and if necessary the surfaces bring the block toabsolutely accurate size and shape and to take care of any warping thatmay have occurred during the hardening process.

The type thus formed, as indicated inFlg. 4, may then be turned upsidedown from the position indicated in that figure and inserted in theretainer dieblock 5 in place of the master die 11, as-illustrated g. 5.The block 18 may be replaced with a similar block 30 provided with arecess 31 corresponding to the recess 19 with its side walls may benormal to the surface of the block 30 instead of at a slight anglethereto as in the case of the recess 19. A block of suitable metal ofthe desired composition for ,the final dies, and of a predetermined sizeas will hereinafter be explained, is then heated to above its criticaltemperature in a reducing or non-o. 'dizing atmosphere as previouslydescribed in connection with the block 20. It is then placed withinately covered with a reducing or non-oxidizing table 13, causingthemetal thereof ground to the recess 31, immedi-- substance and the head14 is then brought towards the table 13, the metal being caused to flowinto the lower portion of the recess 16 and completely filling the same.The tapered side wall 1'? maintains it against lateral spreading duringthis operation so as to insure the metal to firmly and completelyembrace all parts of the surface of the type 21 so that upon separationof the head 14 from the table 13, the metal in the recess 31 isformed'to provide a block 32 having a depression 33 therein exactlycomplementary to .the type 21 except for the fact that when cooled itwill be slightly smaller due to the shrinkage of the metal in coolingand thus, because of the fact that the type 21 is formed to provide fora double shrinkage, is itself formed to provide for a single shrinkage.Likewise the depression 33 will be in exact conformance to thedepression 12 the master die 11 except that it will be of a size twoshrinkages smaller than the size of the depression 12. 7

Only sufilcient metal is placed in the depression 31 to insure completefilling of the depressions 31 and fillable portions of the depression 16when the blocks 15 and 30 are brought together with perhaps theformation of a very slight flash or fin 34. When the block 32 cools itwill automatically free itself from frictional engagement with the wallsof the depression 31 due to its shrinkage and may be easily removed fromthe depression 31. Y

The flash 34 above described, is formed on the sides of the block in aplane considerably below the plane of the surface of the die. Theformation of the flash in this position is highly desirable, because themetal forming it is flowed directly from the main body of the block 32,and there is no tendency to deform the working face of the die. If theflash were formed in the plane of the upper or working face of the die,the metal in forming the flash would flow transversely outwardly fromcavity into the flash and there would be a tendency for the flowingmetal to pull away from the type at the upper edge of the depression 33,thus causing undesirable distortion and an imperfect die cavity. In thiscon- 1 nection it might also be noted that the formation of the flashshould be limited to a line between the approximately parallel edges ofsub-'-- stantially plane side and end faces of the article being formed,that is, there should be no material step in such faces at the point offlash formation, otherwise the action of the dies on the material beingformed may result in folds or pipes in the same.

The block 32 after being removed from the depression 31 is suitablymachined on the side and bottom faces thereof. The sides faces may,"

be machined. square with the top face as in thearticle adjacent thelocation of the die depression or typebeing formed in or on the case ofthe master die 11 and type block 20 and The block is then suitablyhardened in any conventional manner. The retainer die blocks 15 and 30are then replaced by retainer die blocks 35 and 38, these blocks beingprovided with recesses 37and 38 in their opposed faces complementaryinshape to the shape of the block 32 as finally machined, and of the samedepth and contour. One block 32 is then driven into the recess 37 ininverted position and another block 32 is driven into the recess 38 insuch position that the depression 32 therein is exactly opposed to thedepression 33 in the block 32 in the upper retainer die block 35.Knockout pins 39 and 40 are provided in the head 14 and block 35 andhead 13 and block 36 for suitable co-operation with the blocks 32.

A pieceof metal may now be placed between the blocks 32, the retainerdie blocks 35 and 36 be brought together and the piece of metal be thusformed to a shape exactly complementary to the shape of the combineddepressions 33, with the exception that when it is cooled it will be ofa size one shrinkage less than the size of the depressions 33 or, inother words, it will be of a size and shape in exact conformance to thesize and shape of the final article desired.

It will be apparent that with this method of operation being carriedthrough, a single master die 11 may be provided which is made inaccordance with conventional practice. The master die 11 may be employedto make a number of types 21, and each type 21 may be employed to make astill greater number of dies 32, and each set of dies 32 may be employedto make a correspondingly progressively greater number of finishedarticles 10. The formation of the types 21 is accomplished in arelatively cheap and simple manner which eliminates the necessity of anychipping, filing or machining such as would be necessary in forming adie or type in accordance with conventional practice, and the dies 32are correspondingly formed in a simple, cheap and efficient manner atonly a fraction of the cost which would be involved in making an equalnumber of dies in the conventional manner, as in the case of .the masterdie 11. Consequently, where the production is large the cost per set ofdies 32 becomes a negligible figure, whereas were these dies made inaccordance with conventional practice their cost would be a materialfactor in the cost of the final product formed by them.

It will be apparent that by this method the master die 11 will be usedonly at relativel infrequent periods, and in fact so infrequently thatit may never need to be replaced during the manufacture of innumerableobjects such as 10, and furthermore, inasmuch as the master die 11controls the size and shape of the final product, all of the objectsthat are formed from the final dies 32 will be substantially exactly thesame, and will not depend upon the skill of a number of workmen insinking a plurality of dies to the desired shape.

I find that it is extremely important in carrying out the presentinvention that great precautions be taken to prevent any scaling oroxidization of the surface of the successive die parts produced in theprocess between the master die 11 and the final die parts 32, for anysuch sealing or oxidization will necessarily vary the dimensions of thefinal product as formed by the die parts 32 from that contemplated inthe master die 11. Consequently, it is important that not only the metalfrom which the various elements in the progression are made be protectedfrom oxidization during the initial heating to bring them to a workingtemperature, but also that while they are being worked in the press orhammer their surface be protected against oxidization in the mannerdescribed. By this means I am enabled to provide the final die parts 32with a high degree of finish on the surface of their depressions, andmaintain the dimensions of the depressions within extremely closelimits.

The feature of providing the separate retainer die blocks and formingthe dies proper as inserts therefor is also an important feature of thepresent invention, although it is to be understood that the broaderaspects of the present invention are not to be limited thereby. In usingsuch separate retainer die blocks such as 15, 18, 30, 35 and 36, it willbe recognized that the size of the parts in which the depressions areformed or on which the types are formed are relatively small, easilyhandled, and their replacement is relatively more economical than inconventional constructions for the reason that the same relative wasteof material is not present. This may be illustrated, for instance,particularly well in the case of the dies 32, which are the dies whichare subjected to relatively rapid wear due to the fact that they areemployed to form the finished product. When these dies become so worn asto need replacement it is necessary only to replace a relatively smallamount of metal, namely, that included in the die 32, whereas inconventional constructions it will be necessary to scrap an amount ofmetal corresponding with that of both the die 32 and the retainer dieblock 35 or 36, as the case may be.

While I have shown the master die 11 and the type block 20 secured inthe retainer die block 15 by a shrink fit, it is pointed out that thesemembers may equally well be secured within the retainer die block bymeans of a taper fit such as is illustrated in connection with Fig. 6,although I prefer in these particular cases that the die blocks besecured in place by a shrink fit due to the fact that they may be moreaccurately located and retained thanotherwise. The dies 32 may also besecured in place in their respective retainer die blocks 35 and 36 inthe same manner by shrinkage, but due to the fact that I prefer toprovide means whereby the dies 32 may be removed from the respectiveretainer die blocks without necessitating the removal of the retainerdie blocks from the corresponding head or table of the press or hammer,I prefer that these parts be secured in place by the tapered fitdisclosed, whereby they may be easily removed when it is necessary toreplace them by heating the retainer die block, if necessary, with atorch or the like, and simply drive the die therefrom through the mediumof the knockout pins. After these dies are secured in place by a shrinkfit, as in the case of the master die 11 and the type block 20, it willordinarily be necessary to remove the corresponding retainer die blockand by placing it in a bath of molten lead or subjecting to anequivalent heating process without materially heating the insert, causesufficient expansion of the insert retainer block to permit release ofthe insert therefrom.

In accordance with the further phase of the present invention I providea method of altering a die which is once formed, such as the master dieindicated in Fig. 11, so as to provide in the depression thereof metalwhich originally was not present or which has been removed in theformation of the depression. Such an occasion might arise, for instance,were it desired, after the master die 11 is formed, to provide acircumferential groove in the article 10. It will be recognized that insuch a case in accordance with conventional practiceit would benecessary to scrap the die 11 and make a new one. In accordance with thepresent invention instead of scrapping the die 11 I insert such metal,as indicated at 50 in Fig. 7, into it by a welding process and amthereby enable to save the cost of remaking the die, which amounts to aconsiderable saving. The method I employ to add this metal to the diedepression whereby such added metal will be as hard or harder than theoriginal die and will not affect the original die in any mannerwhatsoever outside of changing its shape, is as follows:

I select a welding rod formed of the same metal as the metal of the die11, which is ordinarily a carbon steel or steel alloy, or I may employ awelding rod formed of an alloy which in itself is too hard to permit adie such as the die 11 to be formed therefrom because of difficulty inworking the metal, this last feature being preferable in accordance withthis part of the present invention. I preferably heat the die and thendeposit metal from this welding rod over the area of the die depressionwhich it is desired to build up, by a welding process, in which the atmosphere surrounding the area being welded is deprived of oxygen suchas, for instance, by welding the metal in place by the so-called atomichydrogen method of arc welding. The great importance of using such amethod of welding this material in place is that due to the absence ofany oxygen the carbon content of the metal in the welding rod will notbe materially changed, as it would be in an ordinary welding process,and consequently I may deposit in the die depression a metal which maybe hardened substantially to the same or to a greater degree than themetal of the original die. After sufficient metal has been deposited inthe die depression to form therefrom the desired added volume, thedepression may be reworked to form the added metal into the desiredshape and then, when necessary, the whole die may be reheated andrehardened. Where the material deposited in the die depression is of theso-called air hardening type of steel alloy then it may not benecessary, although it may be preferable in many cases, to reharden theentire die. The use of such an alloy is extremely beneficial in suchcases where the part added is subject to the greatest wear that occursin walls of the die depression, for in such case this particular portionmay be built up of a material which, although too hard to machine theentire die from, will be extremely hard and wear resisting in thecompleted die, and thereb enable the die to be used over a greaterlength of time than would otherwise be possible.

While I have herein described an article to be formed that is identicalon both sides of a central plane, so that two die halves of exactly thesame contour are employed, and consequently but one master die half andone type is necessary to form both, it will be apparent where it isnecessary to provide right and left hand die halves because of thenature of the article to be produced, a separate master die will benecessary to produce the corresponding production die half, and from theforegoing description the method to be followed in such case inaccordance with the present invention, will be obvious to those skilledin the art.

Formal changes may be made in the specific embodiment of, the inventiondescribed without departing from the spirit and substance of the broadinvention, the -scope of which is commensurate with the appended claims.

I claim:

1. The method of forming a large number of dies which comprises: firstforming a master die with provisions for a triple shrinkage in thedepression thereof; impressing masses of metal into said master die toform types; and then impressing said types into masses of metal to formthe dies desired.

2. The method of forming a large number of dies which comprises: firstforming a master die; limiting masses of metal against lateral expansionwhile simultaneously impressing said masses into said master die to formtypes while limiting the formation of the flash to a plane spaced fromthe working faces of the types; and then impressing said types intomasses of metal to form the dies desired.

3. The method of forming a large number of dies which comprises: firstforming a master die; impressing masses of metal into said master die toform types; and then supporting masses of metal against lateralexpansion while impressing said types into the same to form the diesdesired and while limiting the formation of the flash to points removedfrom the faces of the dies.

4. The method of forming a large number of dies which comprises: firstforming a master die; heating masses of metal to above the criticaltemperature of the metal in a non-oxidizing atmosphere; coveringsaidmasses of metal with a coating of reducing material and. thenimpressing the same into said die to form types; hardening said types;and then forcing said types into other masses of heated metal to formdies.

5. The method of forming a large number of dies which comprises: firstforming a master die; heating masses of metal to above the criticaltemperature of the metal and impressing said masses into said master dieto form types; heating other masses of metal to above the criticaltemperature of the metal thereof in a non-oxidizing atmosphere; andprotecting said other masses of metal against oxidization whileimpressing said types thereinto to form dies.

6. The method of forming a large number of dies which comprises: firstforming a master die; heating masses of metal to above the criticaltemperature of the metal in a reducing atmosphere; protecting saidmasses of metal against oxidization while impressing the same into saiddie to form types; heating other masses of metal to above the criticaltemperature of the metal thereof in a non oxidizing atmosphere; and thenprotecting said other masses of metal against oxidization whileimpressing said types thereinto to form dies. f

7. A method of making a die which comprises forcing a type into thesurface of a block of die material of substantially uniform crosssection to form a die depression while the ends of the block areinitially confined and an intermediate zone of the block is unconfined,whereby to cause a portion of the material in an intermediate zone of thblock to flow outwardly to form a flash in the unrestricted zone.

8. A method of forming a die which comprises forming a die impression atone end of a block of substantially uniform transverse cross section andforcing the block to flash in an intermediate zone.

CLAUD L. STEVENS.

